1. Field of the Invention
The present invention relates to a seat reclining apparatus which can lock a seat back to a seat cushion rotatably and at a desired rotational position.
2. Description of the Related Art
As this kind of seat reclining apparatus, there has been proposed a structure disclosed in Japanese Patent Application Laid-Open No. 2004-121508.
A seat reclining apparatus 100 is provided in each of both left and right rear portions of a seat cushion (not shown), and has a pair of base brackets 101 (not shown) fixed to both left and right ends of the seat cushion side, and a pair of arm brackets 102 (not shown) fixed to both left and right ends in the seat back side, as shown in FIG. 1. Reclining lock mechanisms 110 are respectively arranged between the left and right base brackets 101 (not shown) and the arm brackets 102 (not shown). Accordingly, each of the arm brackets 102 (not shown) is supported to each of the base brackets 101 (not shown) so as to be rotatable around a center shaft 103 (not shown). In this case, the center shafts are connected therebetween by a connection pipe (not shown), and both the center shafts 103 (not shown) are integrally rotated.
A spiral spring 104 is arranged in an outer peripheral side of the center shaft 103. The spiral spring 104 is structured such that one end thereof is hooked to the seat cushion side base bracket 101 and the other end is hooked to the seat back side arm bracket 102, and the seat back is biased to a forward reclined position side by a spring force of the spiral spring 104.
The reclining lock mechanism 110 is provided with a base side disc case 111 fixed to the base bracket 101, an arm side disc case 112 fixed to the arm bracket 102 and having an inner peripheral gear 113 formed in an inner periphery, a pair of lock tooth 114 and 114 received in an outer peripheral side within a chamber formed by both the disc cases 111 and 112, a cam plate 115 received in an inner peripheral side within the chamber formed by both the disc cases 111 and 112 and having the center cam shaft 103 fitted thereto, and a pair of lock springs 116 and 116 biasing the cam plate 115 in a counterclockwise direction in FIG. 2 (toward a lock position), as shown in FIGS. 2 and 3. Each of the lock tooth 114 and 114 is supported so as to freely swing around a supporting point 114a, and outer peripheral gears 117 and 117 are formed respectively in outer peripheries of the lock tooth 114 and 114.
A reclining operating lever 120 (shown in FIG. 1) and a forward reclining operating lever (not shown) are attached to a part of the center shaft 103 protruding from the reclining lock mechanism 110 directly or via a connection member, and the structure is made such that a lock of the reclining lock mechanism 110 can be released by operating the operating levers 120 (not shown).
In the structure mentioned above, the reclining lock mechanism 110 is structured such that the outer peripheral gears 117 and 117 of the lock tooth 114 and 114 are engaged with the inner peripheral gears 113 and 113 of the arm side disc case 112 by the spring forces of the lock springs 116 and 116, whereby the seat back is locked with respect to the seat cushion. When a user operates the reclining operating lever 120 so as to rotate the center shaft 103 in a clockwise direction in FIG. 2 against the spring forces of the lock springs 116 and 116, the engagement between the inner peripheral gears 113 and 113 and the outer peripheral gears 117 and 117 is disconnected so as to release the lock. When the lock is released, the seat back is moved to the forward reclining position by the spring force of the spiral spring 104. When the user takes off a hand from the reclining operating lever 120, the reclining lock mechanism 110 becomes in a state of being biased to the lock position side by the spring forces of the lock springs 116 and 116, however, since the lock tooth 114 is in a state of running on an inner peripheral toothless portion 113a continuously formed in the inner peripheral gear 113, the lock tooth 114 is not locked.
When the user draws up the seat back against the spring force of the spiral spring 104 so as to return the seat back at the forward reclined position to a desired reclining position, the lock tooth 114 and 114 slip and move on the inner peripheral toothless portions 113a and 113a, and are locked at a position in which the inner peripheral gears 113 and 113 and the outer peripheral gears 117 and 117 are first engaged with each other.
When returning the seat back at the forward reclined position to the reclining range as mentioned above, the lock is engaged at the forefront position in the reclining range, however, this forefront position is set in a state in which the seat back rises more than a generally used position, it is necessary for the user to again operate the reclining operating lever 120 so as to release the lock of the reclining lock mechanism 110 and set the seat back to the desired reclining position. Accordingly, it is troublesome to operate for returning the seat back at the forward reclined position to the predetermined reclining position, and it can not be said to be good usability.
Accordingly, there has been proposed a structure in which a full memory means for storing a reclining position just before being forward reclined is provided, and the seat back at the forward reclined position is returned to the previous reclining position by the full memory means in the case that the seat back is drawn up so as to be returned to the reclining range (refer to Patent Brochure of Japanese National Publication of Translated Version (Kohyo) No. 2003-516834). Further, there has been proposed a structure in which another lock mechanism than the reclining lock mechanism is provided, and the seat back at the forward reclined position is returned to a predetermined reclining position by the other lock mechanism when the seat back is drawn up to the reclining range (refer to Japanese Patent Application Laid-Open No. 8-182558).
However, since it is necessary that the seat reclining apparatus provided with the full memory means is structured such that all the reclining positions can be stored, there are problems that the structure is complicated, and a cost is increased. Since the full memory means is installed in an inner portion of the reclining lock mechanism, there are problems that it is necessary to employ a major design change, and the full memory means can not be installed to the existing seat reclining apparatus afterward. In addition, in the case of forward reclining the seat back existing at a flat position, the seat back is not locked until it reaches the flat position even by drawing up the seat back so as to return to the reclining range. Accordingly, a usability is not good.
Further, in the seat reclining apparatus provided with the other lock mechanism, since it is necessary to add the independent lock mechanism to the existing reclining lock mechanism, there are problems that the structure is complicated and a cost is increased, in the same manner as the former case. Further, since the load applied from the seat back is received by the other lock mechanism, a strength equal to the existing lock mechanism is required, so that it is necessary to control the strength of the other lock mechanism.